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I have low power cable lighting fitted in my kitchen, 2 cables running in parallel with suspended spots. It has run fine for 8 years then the other day it blew when switching on. I looked at the transformer and there was a blown fuse so I replaced that and it worked.

It worked for about 8 hours then, again when switching on it blew again. I replaced the fuse again, this is a small fuse on the transformer itself. Swapped the bulbs over to LED (from halogen), cleaned the cables to make sure nothing was arcing across from one to another. Then the same happened again it worked for some hours then blew when turning on at the switch.

What I need to know what is likely to be triggering this? I don't understand why it works for a number of hours and then goes. I would expect if it is overloaded or something it would go immediately.

Any ideas would be greatly appreciated.

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Is the power source a simple transformer or a switch mode power supply? Changing the bulbs from halogen to led should greatly reduce the current draw so I doubt the lights are the cause. If you have a power supply, a cap or other component inside it may have aged and changed tolerance enough to cause an internal overload... the power supply went bad.

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  • thanks for the response. Yeah the reason I changed to LED was to reduce the draw so happy that thinking was correct. It is a transformer as far as I know I will look at this.
    – Gurnard
    Commented Nov 25, 2019 at 16:23
  • It was the transformer. I changed the old transformer (seriously heavy halogen lamp transformer weight like it was from the 50s or something) with a new modern one designed for LEDs and everything is working.
    – Gurnard
    Commented Dec 9, 2019 at 15:00
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It's surely due to the huge inrush (100X) current of the leds, try switching the circuit on then plugging the lamps one-by-one.

Also remember that fuses take time to break a circuit if overload is minimal, so the first "few hour work" depletes the fuse enough to weaken it to the point that next switching operation breaks it.

My suggestion is get a 'delayed' (TT) fuse of same amps. (ex: you have a 200mA M, replace it with a 200mA TT )

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    If it's worked fine for 8 years and now all of a sudden blowing fuses, then something is now wrong or changed. Putting in a delay fuse for something that runs fine for a few hours then blows the fuse will do nothing to solve the problem the user is having. In addition, the LEDs would have so much less inrush current than the original halogens that it wouldn't be a consideration at all. My guess is that the power supply is going bad (internal overheating over several hours of usage) after years of use, and I'd recommend replacing the transformer.
    – Milwrdfan
    Commented Nov 25, 2019 at 17:14

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